Embodiments of the present invention relate generally to electromagnetic actuators and, more particularly, to an electromagnetic actuator having a modular construction that provides for easy assembly of the actuator and allows for the use of components therein with relaxed dimensional tolerances, without affecting the performance of the actuator.
Electromagnetic actuators are devices commonly found in power equipment and provide working motion courtesy of an internal electromagnetic field, with the motion of the actuator providing a control or switching function in such power equipment. Electromagnetic actuators provide the movement used for actuation by exposing a free moving plunger or armature to the magnetic field created by energizing a static wire coil. The field attracts the plunger or armature that, in turn, moves, thus providing the required actuation. Varying degrees of actuation functionality can be achieved with an electromagnetic actuator, ranging from simple single-cycle, single-speed actions to fairly sophisticated control of both actuation time and positioning.
One type of commonly used electromagnetic actuator is a permanent magnet actuator, which makes use of one or more permanent magnets and electric energy to control positioning of a plunger therein. Permanent magnet actuators may be configured such that the plunger thereof is held at a stroke position due to magnetic energy of the permanent magnet, with electric energy being applied to the wire coil to move the plunger to a different stroke position.
One drawback common to many electromagnetic actuators is the costs associated with manufacturing and assembling the actuator. That is, many existing actuators include a large number of machined components (e.g., plates, bobbin, permanent magnet, a flux transfer ring, a flux transfer plate, armature, spacer, housing, etc.) of complex shape that require tight tolerances in order to provide for a sufficient holding force in the actuator to properly align/space the components—such that the actuator can function without suffering from reduced performance. The machining of these components with such tight tolerances leads to increased manufacturing costs. Additionally, the complex shape of these components can add to the difficulty of assembling the actuator—leading to an increased assembly/production time for the actuator.
Therefore, it is desirable to provide an electromagnetic actuator assembled from components that have more relaxed tolerances than those required in existing actuators, with such components not affecting the holding force and other performance related characteristics of the actuator. It is further desirable for the components in such an actuator to be assembled in a simple, less time-consuming manner, such that assembly costs of the actuator can be reduced.